Resin bottles, representatives of which are oriented polypolypropylene (OPP) bottles and poly-ethylene terephthalate (PET) bottles, are used in various fields, such as beverages, foods, cosmetics, and so forth. Such a bottle is typically formed in a predetermined shape by biaxially stretch blow molding a resin preform by using a blow molding apparatus in a state where the resin preform is heated to a temperature at which a stretching effect may be achieved. The resin preform has been formed in a bottomed tubular shape by, for example, injection molding.
Known examples of such a blow molding apparatus include the one that uses a pressurized liquid, instead of pressurized air, as the pressurized fluid that is supplied into the preform. As the liquid used in this example, a content liquid, such as a beverage, a cosmetic product, a pharmaceutical product, or the like, that is to be filled into the bottle as a final product may be used. By doing so, the process of filling the content liquid to the bottle may be omitted, and the production process and the configuration of the blow molding apparatus may be simplified.
For example, Patent Literature 1 describes a blow molding apparatus including a blow molding mold to which a preform, after heated to a temperature at which the preform is stretchable, is fitted, a blow nozzle that is fitted to a mouth tubular portion of the preform fitted to the mold, a pressurized liquid supply unit configured to supply a pressurized liquid into the preform through the blow nozzle, and a stretching rod that is freely displaceable in upward and downward directions. By stretching the preform in the longitudinal (axial) direction by the stretching rod and also by stretching the preform in the lateral (radial) direction by supplying the pressurized liquid into the preform, the preform is molded into a bottle having a shape conforming to a cavity of the mold.